The present disclosure relates to an AD converter and an AD converter circuit voltage control method.
When an AD converter circuit is used to perform digital signal processing, it is extremely important to accurately convert an input analog signal to a digital signal, in terms of signal processing following the converter circuit. Normally therefore, an auto gain control (AGC) circuit is disposed at a stage before the AD converter circuit. By doing this, waveform information is not lost and resolution is also not lost. Thus an amplitude level of the analog signal is automatically controlled and an amplitude range of the analog input signal is set to approximately match a dynamic range.
Further, an AD converter circuit (flash type) that is used for reception processing in a high speed wireless communication device divides up a reference voltage into many steps and compares each of the divided voltages, respectively, with an analog input voltage. At the same time, the AD converter circuit encodes results of the comparisons as binary coded digital values. At that time, an analog input dynamic range of the above-described AD converter circuit is determined by the reference voltages. In particular, when broadcast or communication related signal processing is performed, loss can be assumed on a transmission path, and it is therefore essential to keep the analog signal level within a constant range.
Here, as one method to automatically control the amplitude level of the analog signal, technology exists in which difference data (which is obtained by comparing an amplitude value of a signal extracted from a digital output of an AD converter circuit with a predetermined set value) is used to variably set reference voltages that determine the analog input dynamic range of the AD converter circuit (refer to Japanese Patent Application Publication No. JP-A-1-37121 and Japanese Patent Application Publication No. JP-A-09-116435).
By using this technology, the dynamic range of the analog input signal can be caused to match a voltage difference (VOH−VOL) between reference voltages, and a structure is obtained in which a quantization resolution of the AD converter circuit can constantly be utilized to the maximum. Further, as it is not necessary to perform gain control on the analog input signal, an auto gain control (AGC) circuit is not required.